This invention relates to a method and apparatus for detecting leaks in buried pipes using a selected combination of geophysical instruments including ground penetrating radar, electromagnetic induction tools, acoustic sensors, and vacuum excavation.
A method for detecting and locating leaks in buried pipes by radar and induction is disclosed comprising the steps of transmitting a ground penetrating radar signal into a subsurface region, receiving a return radar signal for the subsurface region, processing the return radar signal to create a processed return radar signal, transmitting an inductive signal into the subsurface region, receiving a return inductive signal from the subsurface region, processing the return inductive signal to create a processed return inductive signal, and combining the processed return radar signal and the processed return inductive signal to detect and locate a leak in the subsurface region.
In one embodiment of the invention, the step of processing the return radar signal further comprises using a layer model of the subsurface region. In another embodiment, the step of processing the return radar signal further comprises using multistatic transmitter-receiver geometry. In a further embodiment, the step of processing the return radar signal further comprises detecting an angular change in a straight pipe radar image.
In one embodiment, the step of transmitting an inductive signal further comprises using transient fields. In another embodiment, the step of transmitting an inductive signal further comprises using single-frequency fields.
In a further embodiment, the subsurface region includes a wet soil region and the step of processing the return inductive signal further comprises using a spherical model of the wet soil region. In an additional embodiment, the step of processing the return inductive signal further comprises using a layered model of the subsurface region.
An additional embodiment further comprises the steps of identifying from the processed return radar signal and the processed return inductive signal a first region within the subsurface region having a first wave speed and a first conductivity, identifying from the processed return radar signal and the processed return inductive signal a second region within the subsurface region disjoint from the first region and having a second wave speed and a second conductivity, and detecting a leak in the second region if (1) the second wave speed is less than the first wave speed and if (2) the second conductivity is greater than the first conductivity.
In a further embodiment, the combining step further comprises the steps of identifying from the processed return radar signal and the processed return inductive signal a first region within the subsurface region having a first wave speed and a first conductivity, identifying from the processed return radar signal and the processed return inductive signal a second region within the subsurface region disjoint from the first region and having a second wave speed and a second conductivity, and detecting a leak in the second region if (1) the second wave speed is less than the first wave speed and if (2) the second conductivity is greater than the first conductivity and if (3) a vacuum excavator indicates the presence of a leak in the second region.
Also disclosed is a method for detecting and locating leaks in buried pipes by radar, induction, and acoustic listening comprising the steps of transmitting a ground penetrating radar signal into a subsurface region, receiving a return radar signal from the subsurface region, processing the return radar signal to create a processed return radar signal, transmitting an inductive signal into the subsurface region, receiving a return inductive signal from the subsurface region, processing the return inductive signal to create a processed return inductive signal, receiving an acoustic signal with an acoustic listening device, processing the acoustic signal to create a processed return acoustic signal, and combining the processed return radar signal, the processed return inductive signal, and the processed acoustic signal to detect and locate a leak in the subsurface region.
In one embodiment, the step of processing the return acoustic signal further comprises using a leak-sound enhancer. In another embodiment, vacuum excavation is applied.
In yet another embodiment, the combining step further comprises the steps of identifying from the processed return radar signal and the processed return inductive signal a first region within the subsurface region having a first wave speed and a first conductivity, identifying from the processed return radar signal and the processed return inductive signal a second region within the subsurface region disjoint from the first region and having a second wave speed and a second conductivity, and detecting a leak in the second region if (1) the second wave speed is less than the first wave speed and if (2) the second conductivity is greater than the first conductivity and if (3) the processed acoustic signal indicates the presence of a leak in the second region.
In another embodiment, the combining step further comprises the steps of identifying from the processed return radar signal and the processed return inductive signal a first region within the subsurface region having a first wave speed and a first conductivity, identifying from the processed return radar signal and the processed return inductive signal a second region within the subsurface region disjoint from the first region and having a second wave speed and a second conductivity, and detecting a leak in the second region if (1) the second wave speed is less than the first wave speed and if (2) the second conductivity is greater than the first conductivity and if (3) the processed acoustic signal indicates the presence of a leak in the second region and if (4) a vacuum excavator indicates the presence of a leak in the second region.
Also disclosed is an apparatus for detecting a leak in a buried pipe, comprising a ground penetrating radar transmitter for transmitting a radar signal into a subsurface region, a radar receiver for receiving a return radar signal from the subsurface region, a radar signal processor for processing the return radar signal to create a processed return radar signal, an inductive signal transmitter for transmitting an inductive signal into the subsurface region, an inductive receiver for receiving a return inductive signal from the subsurface region, an inductive signal processor for processing the return inductive signal to create a processed return inductive signal, and a data processor for combining the processed return radar signal and the processed return inductive signal to detect and locate a leak in the subsurface region.
A further embodiment comprises processing circuitry for identifying from the processed return radar signal and the processed return inductive signal a first region within the subsurface region having a first wave speed and a first conductivity and for identifying from the processed return radar signal and the processed return inductive signal a second region within the subsurface region disjoint from the first region and having a second wave speed and a second conductivity, and detection circuitry for detecting a leak in the second region if (1) the second wave speed is less than the first wave speed and if (2) the second conductivity is greater than the first conductivity.
In another embodiment, the radar signal processor uses a layer model of the subsurface region. In a additional embodiment, the radar signal processor further comprises processor circuitry for detecting an angular change in a straight pipe radar image.
In one embodiment, the radar signal processor uses multistatic transmitter-receiver geometry. In another embodiment, the inductive signal transmitter uses transient fields. In a further embodiment, the inductive signal transmitter uses single-frequency fields.
One embodiment further comprises an acoustic listening device receiving an acoustic signal and wherein the data processor further combines the acoustic signal with the processed return radar signal and the processed return inductive signal to detect and locate a leak in the subsurface region. In an additional embodiment, a vacuum excavator is used to verify a leak detected and located by the data processor.
Also disclosed is a method for detecting a leak in a pipe buried in soil comprising determining the conductivity of the soil, determining the wave speed of the soil, selecting a first leak detector and a second leak detector based on the conductivity and the wave speed, applying the first leak detector to the soil to receive a first return signal, applying the second leak detector to the soil to receive a second return signal, and combining the first return signal and the second return signal to detect the leak.
In one embodiment, the first leak detector is a ground penetrating radar system and the second leak detector is an induction system. In a second embodiment, the first leak detector is a ground penetrating radar system and the second leak detector is an acoustic system. In a third embodiment, the first leak detector is a ground penetrating radar system and the second leak detector is a vacuum excavator. In a fourth embodiment, the first leak detector is an induction system and the second leak detector is an acoustic system. In a fifth embodiment, the first leak detector is an induction system and the second leak detector is a vacuum excavator. In a sixth embodiment, the first leak detector is an acoustic system and the second leak detector is a vacuum excavator.